Anode construction



Oct. 12, 1937. 1 sLEplANv 2,095,768

` ANoDE CONSTRUCTION.

Filed June 5, 1933 5% W Joseph S/ep/'an SYM ATTORNEY Patented Oct. 12, 1937 PATENT OFFICE AN ODE CONSTRUCTION Joseph Slepian, Pittsburgh, Pa., assignor to Westinghouse Electric & Manufacturing Company,

East Pittsburgh, Pa., Vania a corporation of Pennsyl- Application June 3, 1933, Serial No. 674,249

l 3 Claims.

My invention relates to an anode structure for a vapor electric device and particularly to a pro-v tective shield for preventing arc-back.

In the operation of vapor electric devices, the 5 chief dilliculty has been the tendency to arc-back or backre on the inverse half cycle. In order to prevent such backres, it has been customary to provide deionizing grids in the arc path and to provide' shields adjacent tol the anode heads. l These grids and shields present surfaces upon which the positive ions and electrons discharge and become neutralized so that a rapid deionization of the space adjacent to the anode head takes place immediately after the end of a conducting 15 period. V

However, when metallic grids are used, an inverse arc may establish to the grid itself and from there strike to the anode head.

It is an object of my invention to provide an 20 anode construction in which the danger of arcback will be minimized.

The anode according to my invention comprises a suitable enlarged anode head of conducting material suspended from the anode stem.

25 A suitable insulating bushing is provided on the anode stem from which is suspended a shield usually of metal which substantially surrounds the anode head. The open end of the shield is provided with a grid of quartz or other suit- 30 able non-conducting material. The insulating grid will serve to discharge ions and electrons in substantially the same manner as a metallic grid but because of the insulating nature of the material, substantial currents cannot flow into the 35 grid at one point and out at another sothat an arc to the insulating grid cannot form.

Other objects and advantages of my invention will be apparent from the following detailed description taken in conjunction with the accom- 40 panying drawing in which the single gure is a sectional elevation of an anode embodying my invention. Y

The anode construction according to my in- Vention comprises a suitable anode head I com- 45 posed of conducting material such as graphite secured to an anode stem 2 preferably of ferrous material. Surrounding the anode stern is a cornpound insulating bushing 3 such as disclosed in copending application Serial No. 588,915, i-lle 50 January 26, 1932.

Suspended from the outer portion of the insulating bushing is a substantially tubular shield 5 preferably of sheet metal. A suitable cap 6 attached to the bushing and the tubular shield 55 substantially closes the space between the tubu- (Cl. Z50-27.5)

lar shield and the insulating bushing. The open end of the shield 5 is closed with a suitable grid l 0 preferably composed of concentric rings of insulating material such as quartz or aluminum oxide known in the trade as alundum. The in- 5 sulating grid is held in place by suitable mechanical fastenerssuch as the cross bolts l I which are provided with suitable insulators l2.

Since the space between the grid and the anode, and spaces in the grid itself must be deionized by diffusion of the ions to the grid Walls, it is clear that this dionization will be most rapid if these spaces are made of small dimensions. Hence the grid is placed in close proximity to the Working surface of the anode head l.

In operation, the insulating grid causes the space between it and the anode to be almost completely deionized, while the space between the grid and cathode remains conducting due to ions coming from the arc to other anodes. The inverse voltage on the anode is thus impressed almost entirely upon this deionized space between the anode and grid, but because of the breakdown characteristics of short spaces in vacuum, this space is well able to withstand this voltage. If for any reason a backre cause should exist on the insulating grid I0 the non-conducting -character of the material will prevent the formation of an arc to the grid and thus nothing will occur to reionize the space between grid and anode. In this manner the insulating grid prevents the formation of inverse arcs or backres in the vapor electric device.

While I have shown and described a specific embodiment of my invention, it is apparent that changes and modifications can be made therein without departing from the spirit and scope of my invention. I desire, therefore, that only such limitations be imposed as are embodied in the accompanying claims or may be necessitated by the prior art.

I claim as my invention:

l. An anode construction for a vapor-electric device comprising an anode Stem, an enlarged anode head on said stem, an insulating bushing surrounding said stem, a metallic shield supported by said insulating bushing and substantially surrounding the lateral surfaces of said anode head, a grid shaped deionizing member of insulating material supported by said shield in closely spaced deionizing position with respect to the lower or active surface of said anode head.

V2. An anode construction for a vapor-electric device comprising an anode stem, an enlarged anode head on said stem, an insulating bushing surrounding said stem, a metallic shield supported by said insulating bushing and substantially surrounding the lateral surfaces of said anode head, a grid shaped deionizing member of quartz supported by said shield in closely spaced deionizing position with respect to` the lower or active surfaceof said anode head.

3. An anode construction for a Vapor-electric device comprising an anode stem, an enlarged anode head on said stem, an insulating bushing surrounding said stem, a metallic shield substantially surrounding the lateral surfaces of said anode head, a perforated deionizing member of insulating material supported by said shield in closely spaced deonizing position with respect to the lower or active surface of said anode head.

' JOSEPH SLEPIAN. 

